1. Field of the Invention
The present invention pertains to a load balancing system and method which, for instance, are suitably employed in a storage system.
2. Description of the Related Art
Conventionally, as one application function installed in a storage device, there is a copy function for creating a mirror of a logical device (this is hereinafter referred to as a “LDEV”) in the same storage device without going through a host system as the higher-level device (this is hereinafter referred to as an “internal mirror copying function”).
Further, as another application function installed in a storage device, there is a function of virtualizing the LDEV set in an external storage device (this is hereinafter referred to as an “external LDEV”) and providing it to the host system while making it seem that it is a LDEV in its own storage device (this is hereinafter referred to as an “internal LDEV”) (this hereinafter referred to as an “external connection function”).
In order to balance the load of a storage device that is not using the external connection function, it is standard to adopt the method of migrating (copying) data to a separate storage device via the host system. Nevertheless, when the storage device is using the external connection function, since it will suffice to merely switch the mapping to the external LDEV to a LDEV in another storage device, the load of the storage device can be balanced relatively easily.
Incidentally, Japanese Patent Laid-Open Publication No. 2004-145855 discloses technology for balancing the load of a storage device equipped with a so-called remote copy function which overwrites data among a plurality of storage devices located in physically distant locations without the intervention of a host system.